I have some problems in simply performing FFT in Origin 8. In Version 7.5 it was enough to define a new column (set as x) and to let the time increments calculate by simply i/(Sample Rate). And then fft of a y-column could be performed. This seems not to work anymore. Nevertheless, in V8 in the fft options you can set a sample intervall manually. Unfortunately in seconds. Instead of this, is there no possibility to enter this value in Hz. So let's say 300 Hz. It is even not possible to enter something like '1/300'. It is not practical in my opinion always to calculate manually the reciprocal value of the sample interval. Or how do you perform a simple fft from data columns in the new version without holding a calculator in your hand ;-)?
If Origin does not find an associated X then the FFT dialog assumes row index and gets an interval of 1. Thus you are forced to break out the calculator to find your interval. I believe in your case Origin is not finding the X because it is to the right of your Y.
In the special case where a worksheet has only one X column, Origin plotting is smart enough to look to the right for the X column. (Normally, Origin likes the left to right sequence of X-Y-Z.)
We will make the FFT dialog use this same logic to find the X interval even when the worksheet has the reverse order, but you will need to use a workaround in the meantime.
Use the Column : Move Columns menu option to move your X column to the left of your FFT (Y) data.
Thank you very much. With the x-column on the left side it works fine. One more thing I would like to mention is the translation in the german version of the word 'Frequency'. It is translated with 'Häufigkeit' which is similiar to the frequency term from statistics. It should be 'Frequenz' which corresponds to the frequency term from signal analysis.
Sampling Intervall in [Hz] in FFT
Posted - 06/04/2009 : 05:56:06 AM
